When the truth is out there, continued 'ignorance' equals 'ignoring' that which is there to be known.

The "why?" is that they are ignorant of the nature of their self and the human condition of being part and parcel of the whole, in-separately connected with the totality. Personal desires are mistaken as the summum bonum in warped worlds.

It is the false understanding of "self" that underlies the ability to ignore other selves as unworthy.
It is the false understanding of self that births selfishness and the motivational need to NEVER be wrong.
They know what they are doing but ignore the harm they do.

Too many exist in ignorance of dharma, right path, ethics, morality and kindergarten sharing.
Having been taught right from wrong, they continue ignoring the results of wrong actions while believing only they are deserving.

One who correctly understands "self' is capable of humility and change and thus is not attached to the tatters of worn-out beliefs. Such ones willingly redress the self in other than the 'emperor's new clothes.